The present invention relates to unsaturated fatty acyl moieties of free fatty acids, glycerides and other esters, in which sites of ethylenic unsaturation are stabilized via conversion to other moieties, including lactone, ketone, dihydrofuran, and vinyl groups. Compounds that are, or include, partial or complete lactone, ketone, dihydrofuran, or vinyl analogs of fatty acyl moieties are also contemplated, in which lactone, ketone, dihydrofuran, or vinyl moieties are linked into or pendant from a hydrocarbon chain.
Vegetable oils have some characteristics that favor their use as, or as a component in, lubricant formulations, hydraulic fluid formulations, and dielectric fluid formulations, including dielectric cooling fluid formulations. The long chain fatty acid and ester functionality of vegetable oils gives them good characteristics with respect to lubricity. They also have good resistance to passing electrical currents (dielectric strength). Their biodegradability and status as a renewable feedstock also give them advantages over petroleum-based products.
Vegetable oils, however, have shortcomings that have limited their use in lubricants, hydraulic fluids, and dielectric fluids, including dielectric cooling fluids. Vegetable oils have relatively low oxidative stability and relatively high pour points. Vegetable oils also tend to solidify when held at their pour points, unlike petroleum-based products. The oxidative stability problem is due to sites of ethylenic unsaturation (i.e. C═C bonds) in the hydrocarbon chains of fatty acyl moieties (i.e. RC(O)—, where R is an ethylenically unsaturated hydrocarbon moiety) of vegetable oils, with fatty acyl moieties containing more than one ethylenic double bond being particularly prone to oxidation.
These shortcomings have been addressed in many ways, such as additive packages containing antioxidants and pour point depressants and the use of synthetic esters, poly alpha olefins or other compounds as diluents to improve pour point.
The oxidative stability problem has been more directly addressed by partial hydrogenation to reduce the number of ethylenic double bonds, partial polymerization (heat bodying), breeding or artificial genetic modification of the oil-producing plants to increase the level of monounsaturated fatty acids in the oil, or hydroxylation followed by esterification of short chain fatty acids to the free hydroxyl groups (U.S. Pat. No. 6,583,302 B1 Erhan et al). Esters have been made with fatty acids and on the fatty acid chains of hydroxylated fatty acids (U.S. Pat. No. 6,316,649 B1 Cennack et al). In addition some work has been done with the formation of secondary ethers (U.S. Pat. No. 6,201,144 B1 Isbell et al). Free radical chemistry has been used to graft antioxidants into rubber (U.S. Pat. No. 4,739,014 Parks et al).
U.S. Pat. No. 4,011,239 (Heiba, et al) discloses selective reactions of free radicals with olefins in the presence of an ion of Mn, V, or Ce.
U.S. Pat. No. 6,201,143 B1 teaches making a polymer using meadowfoam oil fatty acids or meadowfoam oil as a starting material to form monomers with fatty acids with vinyl groups and making a polymer out of them. That patent mentions that the resulting polymer has enhanced oxidative stability.
Other documents possibly of interest include U.S. Pat. No. 4,014,910 (de Klein); U.S. Pat. No. 4,119,646 (Heiba, et al.); U.S. Pat. No. 4,175,089 (Heiba, et al.); U.S. Pat. No. 4,328,363 (Heiba, et al.); U.S. Pat. No. 4,736,063 (Coleman, et al.); U.S. Pat. No. 4,380,650 (Coleman, et al.); U.S. Pat. No. 4,158,741 (Goi, et al.); U.S. Pat. No. 6,201,143 B1; Anatoli Onopchenko and Johannn G. D. Schulz, Oxidation by Metal Salts, J. ORG. CHEM., Vol. 57, No. 16, 1972 pg 2564-2566; Harold E. De La Mare, Jay K. Kochi and Frederick F. Rust, Oxidation and Reduction of Free Radicals by Metal Salts, J. AMER. CHEM. SOC., May 20, 1963, Pg. 1437-1449; E. I. Heiba and R. M. Dessau, Oxidation by Metal Salts. VIII. The Decomposition Of Ceric Carboxylates In The Presence Of Olefins And Aromatic Hydrocarbons, J. AMER. CHEM. SOC., 93:4 Feb. 24, 1971 p. 995-999; E. I. Heiba, R. M. Dessau and P. G. Rodewald, Oxidation by Metal Salts. X One-Step Synthesis Of (Gamma) Lactones From Olefins, J. AMER. CHEM. SOC., 96:26 Dec. 25, 1974 pg 7977-7981; Barry B. Snider, Manganese(III)-Based Oxidative Free Radical Cyclizations, CHEM. REV. 1996, 96, 339-363; I. E. Heiba, R. M. Dessau, A. L. Williams; P. G. Rodewald, Substituted Gamma Butyrolactones From Carboxylic Acids And Olefins: Gamma-(n-octyl)-gamma-butyrolactone, ORGANIC SYNTHESES, COLL. Vol. 7, p 400 (1990) Vol. 61, p. 22 (1983) and Ursula Biermann et al., New Syntheses with Oils and Fats as Renewable Raw Materials for the Chemical Industry, in BIOREFINERIES—INDUSTRIAL PROCESSES AND PRODUCTS: STATUS QUO AND FUTURE DIRECTIONS, Vol. 2 (Birgit Kamm, Patrick R. Gruber & Michael Kamm eds., 2006).
All the above patents and publications are incorporated by reference in their entirety.